Hi everyone,
My front nearside Low beam headlight has recently stopped.
Having replaced the bulb and it not working, I tried the "not working" bulb in the drivers side and it worked. Also placing the known working bulb in the nearside, that doesnt work.

Yesterday I got in the car and the bulbs were both working, until I reached my destination and turned off the ignition. When trying the lights again, the nearside was not working.

I am suspecting it might be Ballast?

Could anybody tell me whether I might be correct and if so where the ballast is located in a 12 plate J10 facelift. Also is there a check I can do to prove it?

I was concerned that might be the case and that it might not be Ballast Thank you for the clarification.
Looking at the wiring diagrams online it looks like it is either a faulty earth (thinking this is doubtful due to it being a shared earth with the main beam) or a faulty live.
I suspect that the live comes from the ECU somewhere.
I have swapped fuse 45 + 46 (left and right LO headlights 15A fuses). They are both fine and the fault stayed in the nearside once swapped. Without a multimeter I think I am out of options but to send it to a garage for a costly investigation?